696 did a nice one in 06. Won them the Innovation in Control Award. Here's a pic.
http://www.chiefdelphi.com/media/photos/23631. It was comprised of 4 rings. Inner and outer, and then an upper and lower of each. Each ring had a 45 degree chamfer milled around it. When placed together, inner, outer, upper, and lower, these chamfers would form a diamond shape. In this groove rode alternating steel and delrin balls. This groove gave us 4 points of contact on the balls, so that the turret could be loaded in any direction (axial, radial) and still rotate buttery smooth. It's large diameter made it quite stable.